This invention relates to serial printers and, more particularly, to serial printers of the type comprising a frame; a platen mounted to the frame for rotation about its axis, the platen capable of supporting and advancing record material through the printer; a carriage assembly having a printing member supported thereon, the carriage assembly being supported for movement along a printing path adjacent the platen; a motor mounted to the frame; means for converting the rotary motion of the motor to movement of the carriage assembly along the printing path, the converting means including a cable mounted at either end to the frame; and means for tensioning the cable.
Serial printers of the above type are entirely well known in the art and examples thereoof are disclosed in U.S. Pat. Nos. 3,872,960 and 4,091,911. Commercial printers of this type include the HyType I and II daisy-wheel printers manufactured by Diablo Systems, Inc. of Hayward, California.
Up until now, the cable tensioning means utilized in serial printers of the above-described type employed various types of springs such as compression, extension, constant force compression and flat. An example of a compression spring tensioning device is disclosed in the two above-identified patents. Although these prior art cable tensioning means have worked reasonably well, they are somewhat deficient in providing a substantially constant tension as the cable stretches and wears through prolonged use.
Accordingly, it would be desirable to provide a serial printer of the above-described type wherein the cable tensioning means is capable of maintaining a substantially constant cable tension notwithstanding the effects on tension caused by cable stretching and wearing and the like. It would also be desirable to be able to isolate the tensioning means from the normal operating loads experienced by the carriage assembly's drive system.